Introduction to special issue: Contextually valid assessment of executive functions in the era of personalized medicine

For nearly three decades, measures of executive functioning (EF) have been criticized for having poor ecological validity (Burgess et al., 1998; Sbordone, 2010; Shallice & Burgess, 1991; Shallice & Burgess, 1991). The main premise of this criticism is that performances on measures of EF do not adequately predict patients’ ability to function in daily life. To be clear, much research supports the notion that EF as a neurocognitive domain relates to daily functioning (Avci et al., 2018; Bell-McGinty et al., 2002; Boyle et al., 2004; Burton et al., 2019; Cahn-Weiner et al., 2002; Cahn-Weiner et al., 2000; Grigsby et al., 1998; Jefferson et al., 2006; Kraybill & Suchy, 2011; Kraybill et al., 2013; Mariani et al., 2008; Marshall et al., 2011; Puente et al., 2016; Secrest et al., 2000; Woods et al., 2019), and that measures of EF do a better job of predicting daily functioning than measures of other neurocognitive domains (Cahn-Weiner et al., 2000). Nevertheless, the abundance of literature showing statistical significances in group studies has not been helpful to clinicians who are tasked with making decisions and recommendations about each of their patients individually. In other words, rather than group statistics, clinicians want to know whether the one patient they just assessed is safe to drive (Bernstein et al., 2019), can live independently (Gold, 2012), or can return to work (Rabin et al., 2005).

To address the concerns about ecological validity of our traditional EF tests, many researchers have endeavored to develop new tests that more closely resemble the real-world, often by employing virtual reality or real-world-like scenarios (Burgess et al., 2006; Dawson et al., 2009; Jovanovski et al., 2012). These efforts have had the unintended consequence of fueling widespread conflation of ecological validity with face validity—in other words, in the neuropsychological vernacular, it has become a virtual truism that if a test looks like cooking, driving, bill-paying, etc., then it must be ecologically valid. However, there is little if any evidence that increasing a test’s face validity improves its ability to predict real-world functioning. In fact, we have recently demonstrated that a test that is highly face-valid (i.e., the Pillbox Test; Zartman et al., 2013) did less well predicting actual real-world functioning (i.e., medication management at home over the course of eight weeks) than did a test of EF that had no discernable face validity (Ziemnik & Suchy, 2019). These findings suggest that the efforts of our discipline to increase the face validity of our measures may not ultimately yield the desired results.

The present special issue offers an alternative approach to improving the validity of our predictions about daily functioning by following the principles of personalized medicine. The goals of personalized medicine, as applied to clinical neuropsychology, are to tailor our methodology (i.e., instrument selection, score interpretation, predictions about daily outcomes, etc.) to individual patients and, importantly, to individual situations. Admittedly, aspects of personalized medicine have always been applied in the course of neuropsychological evaluations (e.g., taking the patient’s demographics into account, selecting a test battery based on the referral question, etc.); however, a number of contextual factors, particularly those that fluctuate from day to day or even moment to moment, have been largely ignored. This special issue focuses on the role of both stable and fluctuating contextual factors that are unique to individual patients and individual situations, with the goal of facilitating more nuanced interpretation of test data. Articles in this special issue are presented in three sections: (1) Theoretical Innovations: Redefining and Assessing Executive Functions, (2) Contextual Factors: Ramifications for Test Score Interpretation, and (3) Daily Functioning: Contextual Factors and Targets for Intervention.

Theoretical innovations: redefining and assessing executive functions

The articles in this section of the special issue essentially argue for a paradigm shift in how executive functioning is conceptualized, along with a paradigm shift in how it is assessed. The first article (McKinney et al., 2020) proposes that EF should be conceptualized as a fluctuating entity, and, in fact, that the degree of intra-individual variability (IIV) could be seen as a core aspect of the EF construct. Of course the notion that IIV is a relevant aspect of performance is not new (Costa et al., 2019). However, McKinney and colleagues take the prior conceptualizations a step further by proposing the notion of “coupling” between contextual factors and performance fluctuations, firmly anchoring IIV in the Dynamical Systems Theory (Shapiro, 2015), and providing an overview of technological advances that lend themselves to capturing IIV not only in the doctor’s office, but also at home.

The second article in this section (Mulligan et al., 2020) builds on some of the same principles introduced by McKinney, forging an empirical investigation of different times scales (from seconds to days and weeks) along which adaptation (i.e., learning, practice) of EF performance takes place. Similarly, the third article (Schmitter-Edgecombe et al., 2020) in this section illustrates empirically how the very same principles put forth by McKinney and colleagues can be applied to clinically relevant questions, namely assessment of EF and its association with daily functioning. The results of this study suggest that IIV is a reflection of the degree to which one is vulnerable to the deleterious impacts of various contextual factors in daily life.

Contextual factors: ramifications for test score interpretation

The next section of the special issue examines several of the many potential contextual factors that need to be considered when interpreting test scores. The first article in this section (Niermeyer & Suchy, 2020a)¹ once again invokes the notion of coupling (as introduced by McKinney and colleagues earlier in this issue) between contextual factors and test performance, illustrating that non-restorative sleep, experience of pain, and the need to engage in burdensome emotion regulation all impact test scores, both singly and in aggregate. Importantly, taken together with the findings from Schmitter-Edgecombe et al. (2020), a potential personalized-medicine model begins to emerge, wherein a clinician could determine the degree to which a patient is vulnerable to the influence of contextual factors by assessing IIV, and then use that information to determine the degree to which the patient’s obtained scores should be corrected for a night of bad sleep or experience of pain.

The second article in this section (Singh et al., 2020) makes a similar point, that is, that the degree to which a patient reacts behaviorally to subtle differences in test administration depends on the patient’s psychiatric status. Specifically, this study found that patients’ psychological characteristics determined which mode of test administration (by a computer vs. by a person) deleteriously affected performance, and which aspects of performance were uniquely vulnerable. Lastly, the third article in this section (Moerman – van den Brink et al., 2020) illustrates that the degree to which known associations between EF and outcomes will become manifest depends on the level of overall cognitive status. Specifically, among patients with severe impairment, diminished cognitive differentiation among domains may prove EF assessment moot. In this study, simple mental status, not EF, was the best predictor of psychiatric symptoms (i.e., apathy) in a sample of severely impaired patients diagnosed with Korsakoff’s syndrome, despite the fact that prior research has shown a robust association between EF and apathy (Bertrand et al., 2019; Butterfield et al., 2010).

Daily functioning: contextual factors and targets for intervention

The third section takes the notion that contextual factors impact test performance a step further, demonstrating that such factors can similarly impact various aspects of daily functioning, such as medication management, the ability to maintain independence, or risk for falls. Additionally, articles in this section either implicitly or explicitly suggest that contextual factors and their associations with EF offer promising targets for interventions. The first article in this section (Sheppard et al., 2019) illustrates that EF mediates the well-known inverse association between age and independent daily functioning. Importantly, from among several different cognitive variables, prospective memory (as an aspect of EF) emerged as the strongest mediator of daily functioning. These results suggest that interventions that target prospective memory, such as electronic reminders, may be more effective than interventions that aim to improve episodic memory, or, alternatively, that prospective memory should be carefully assessed prior to assigning older adults who struggle in daily life to an intervention program. The second article in this section (Niermeyer & Suchy, 2020b)¹ similarly points to EF as the mediator between daily stressors and falls among older adults. While it is well recognized that older adults are at an increased risk for falls under certain stressful circumstances, such as when experiencing pain (Stubbs et al., 2014) or when not getting enough sleep (Stone et al., 2008), the results of this article demonstrate that engagement in burdensome and maladaptive emotion regulation strategies also impacts fall risk. The take-home message from this study is that interventions that target emotion regulation styles may prove beneficial with respect to improvements in EF, while also mitigating the risk of falls and physical injuries.

In contrast to the first two articles in this section, the next two articles demonstrate that the association between contextual factors and outcome is not mediated, but rather is moderated, by EF. Specifically, Suchy et al. (2020)¹ found that complexity of daily life has an impact on the ability to take one’s medications correctly, but only among older adults whose EF is below average. The findings of this study have direct implications for interventions and psychoeducation: Individuals whose EF is poor would be well advised to simplify their lives and increase structure so as to avoid taxing limited EF resources that are needed for medication management. A moderation effect is also reported by Kinsella et al. (2020) who found that a memory intervention among older adults diagnosed with Mild Cognitive Impairment was most effective for those with better EF. Results of this study could facilitate tailored deployment of intervention resources to those patients who are most likely to benefit. The final article of this special issue (Quistberg & Mueller, 2019) reported that different aspects of EF (inhibition and working memory) prospectively predicted future behavioral difficulties (externalizing and internalizing) in preschool children. Importantly, the relationship was reciprocal, also showing that behavioral problems precipitated further deterioration in cognition. These findings show the need for multipronged approach to interventions, targeting both cognition and behavior, which affect each other in a reciprocal fashion. Importantly, screening for EF weaknesses early may be able to identify children who are at risk for developing psychopathology before detrimental behavioral symptoms develop.

Yana Suchy
Department of Psychology, University of Utah Salt Lake City, USA
[email protected]

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes

1 Some articles in this issue were co-authored by Yana Suchy, who is the Editor-in-Chief of The Clinical Neuropsychologist (TCN). As a Taylor & Francis policy, and in compliance with publishing ethics, no TCN editors (EIC or Associate Editors) have access to any aspects of the review process pertaining to articles on which they are an author/co-author. For the purpose of these submissions, Dr. Anne Dull Baird, a TCN Associate Editor, assumed 100% responsibility for the processing and editorial decisions regarding those manuscripts.